Hydraulic cylinder actuator baffles



Feb. 15, 1966 J. s. ABER 3,234,854 HYDRAULIC "CYLINDER ACTUATOR BAFFLESFiled Dec. 5, 1965 30A 12 30 30c 24 30B 300 INVENTOR JOSEPH s. ABERUnited States Patent Qfitice 3,234,854 Patented Feb. 15, 1966 3,234,854HYDRAULIC CYLINDER ACTUATOR EAFFLES Joseph S. Aber, Philadelphia, Pa.(439 Argyle Road, Drexel Hill, Pa.) Filed Dec. 5, 1963, Set. No. 328,2851 Claim. (Cl. 91-4) This application is a continuation-in-part ofapplication 317,164, filed October 18, 1963, for Hydraulic CylinderActuator.

This invention relates to an actuator for a hydraulic cylinder. Moreparticularly, it relates to the bafiles in actuating means for ahydraulic cylinder in which gas pressure is used in combination withhydraulic fluid.

In certain types of hydraulically actuated cylinders, a reservoir ofhydraulic fluid is provided with access to the cylinder on each side ofthe piston Within the cylinder. A differential in the gas pressureapplied to the surfaces of the fluid in the cylinders results in anunbalanced for-ce on the opposing faces of the piston and the cylinderis thus actuated. Accurate positioning of the piston, and carefullycontrolled movement of it are desirable in certain applications. In manyapplications, it is important that the position and movement of thepiston be held to close tolerances, and that its movement be highlyresponsive to applied control.

Typically, the hydraulic fluid is oil and the gas is air: the terms oiland air are used throughout this specification as terms of convenience,but it is understood that all gases and hydraulic fluids known orsuitable for the use in such hydraulic systems are contemplated withinthe scope of the invention.

A seemingly straightforward system in practice presents somecomplications that adversely affect its desirable characteristics.Sudden high pressure bursts of air impinge on the exposed surface of theoil in a reservoir and it has been found that there is a tendency toentrap air bubbles in the oil, in a manner explained below. Thiscondition reduces the sensitivity of the system. It has also been foundthat when it is desired to hold the piston at a stable position byadmitting equal air pressures to each reservoir, there may still be atendency for the piston to creep because of difierentials in theeifective pressure on the surface of the oil in the two reservoirs dueto differences in the characteristics (such as length) of the linesthrough which the air is supplied. Ex-pedients have been practicedtoward the end of reducing or eliminating these problems, and thepresent invention is an improvement over other such expedients.

The present invention has several advantages over the baffle typestructure disclosed in my co-pending application, of which this is acontinuation-in-part. Briefly, these advantages include less criticalityof centering, better distribution of fluids entering and leaving theactuator cylinder, lower terminal velocity of fluids entering theactuator cylinder, more prevention of aeration of the hydraulic liquid,less splashing, and in general better sensitivity.

Prior means to prevent the entrapment of air in the oil are shown, forexample, in United States Patents 2,683,463 and 3,053,233.

It is an object of this invention to provide a hydraulic cylinderactuator.

It is another object of this invention to provide improved bafllingmeans for actuating means for an airoil hydraulic cylinder system.

It is yet another object of this invention to provide an air-oilreservoir system adapted for use with a hydraulic cylinder, in whichmeans are provided to prevent churning of the air and oil, and to reduceunwanted pressure differentials.

It is yet another object of this invention to provide means in ahydraulic cylinder oil reservoir to distribute the flow of incoming gasso as to avoid mixing with the oil.

Other aims and objects of this invention are made apparent in thefollowing specification and claims.

The invention is best understood in connection with the drawing. FIGURE1 is a schematized cross-sectional elevational view of a hydrauliccylinder and its actuating system. FIGURE 2 is a cross section of theline 22 from FIGURE 1.

A conventional hydraulic cylinder generally designated is shown. Thiscylinder 50 is provided with a piston 53 to which is affixed a pistonrod 54. The piston is free to move axially within the cylinder 50 in theordinary way. Hydraulic fluid, generally oil, 60, is provided inside thecylinder 50 on both sides of piston 53. Oil lines 52 and 51 open intothe cylinder on opposite sides of piston 53.

The actuator is generally designated 100. It comprises a base 40 and atop 30. These elements are preferably made of machined metal stock, suchas brass, and may typically be rectangular blocks of metal, machined orotherwise fashioned to provide recesses and passages therethrough asindicated in the drawing. It is understood that the actuating means,which constitutes the subject of this invention, is illustrated as muchlarger than the hydraulic cylinder, which is included in the drawingonly to show a complete system. In actuality, the scale of the cylinderand actuating means might be reversed.

A pair of reservoir cylinders 34 and 35 are provided between top 30 andbase 40. As shown, these hollow cylinders may be mounted between the topand the base by being fitted into circular grooves milled or otherwiseformed in the facing surfaces of the top and base, respectively. Thus, areservoir cylinder together with its closed top and bottom formed bypart of the top 349 and base 40, respectively, may be described as areservoir. It is understood that tight seals are provided at all jointsand that the shape of the reservoir is not critical to the invention.The exact dimensions of the reservoirs are not critical to theinvention, but the typical field of application of this inventionnormally lies in reservoirs whose reservoir cylinders have diameters ofone-inch or more, with the other dimensions of the reservoir typicallyin somewhat the same proportions shown in the drawing, although notnecessarily so. The reservoir cylinders 34 and 35 may be made of metal,or may be made of transparent plastic or glass. There is an advantage inproviding the pair of cylinders of transparent material when they aremounted in the close side-by-side relationship on a common base asillustrated in the preferred embodiment shown. The advantage is that thediiferential in oil levels between the two cylinders is immediately andeasily visible to the eye of the operator. It is then apparent that thisdifferential is an index to the position of the cylinder. The reservoircylinders 34 and 35 may be provided with etched, engraved or othermarkings to provide index marks so that levels may be readquantitatively. Alternatively, linear measuring means may be provided toquantitatively measure the difference between the levels. Such a meansincludes a simple ruler with provision for raising or lowering itbetween the two reservoirs. It is also apparent, if the level of the oilin each cylinder is set so as to be the same when the piston 53 is insome central or standard position, that an immediate quantitative orqualitative visual indication is given as to what side of the standardposition the piston 53 is at any moment, and how far it is displaced.Thus, in the drawing, the oil 60 in reservoir cylinder 34 stands higherthan in cylinder 35 and this corresponds to a displacement of piston 53toward the left of hydraulic cylinder 50.

The oil lines 51 and 52 communicate respectively to reservoir cylinders34 and 35 through the respective bores MlB through base 41 Air lines and24 communicate through certain connecting means described belowrespectively to reservoir cylinders 34 and 35. A preferred form of thecommunieating means is illustrated. Air bores A and 30C are provided intop 30 to respectively receive air lines 25 and 24 as shown. These airbores may be horizontally drilled or otherwise formed in the top 30.Considering first the structure connected to air bore 311A in reservoir34, a dispersing head 10 is provided. The head 10 has an extension tube12. This tube 12 has an outside diameter such that it fits snugly intothe vertical air bore 30B, which is drilled or otherwise formed in top30, and which communicates with the interior end of horizontal air bore30A. The vertical air bore 30B is centered within the milled orotherwise formed circle on the underside of top 30 that accommodates thewalls of reservoir 34. The tube 12 may be positioned in bore 30B by anyconvenient known means, such as by matching threads, locking screws,force fit, or camming surfaces, for example.

The main body of dispersing head 10 is thus supported inside reservoircylinder 34-. In the same manner, a dispersing head 10 is supportedwithin reservoir 35, by having its extension tube inserted into avertical air bore 30D. The description in connection with air bore 30Bis also applied to air bore 30D. The lower dispersing heads 10 inreservoirs 34 and 35 also have their extension tubes fitted into theappropriate bottom air bores B, as illustrated. In the case of thebottom or lower heads 10, which are aflixed to base 40, there is, ofcourse, in the illustrated embodiment, no horizontal air bore. Each boreadapted to receive a dispersing head is centered within the groove orother boundary of the walls of its respective reservoir cylinder.

The air valving and supply means are conventional in themselves and arenot shown in detail in the drawing. The arrows pointing in and out ofair lines 2 and 25 do show the direction of the air. When it is desiredto move piston 53, compressed air is supplied to one reservoir, forexample, to reservoir 34; the air moving in the direction of the solidarrow at air line 24. At the same time, air line 25 may be vented, or asis often the case, connected to a vacuum; the solid line in connectionwith air line 25 shows the direction of air movement. Under thecondition just described, the level of oil 60 in reservoir 34 wouldfall; the oil level in reservoir 35 would rise, and piston 53 inhydraulic cylinder moves to the right. The dotted line arrows in FIGURE1 show the movement of air in the respective air lines when the pistonmovement is reversed.

In use in systems of the type herein described, where operatingpressures are typically of the order of between 90 and 175 pounds persquare inch, there is a sudden burst of air admitted to a reservoir.This sudden burst tends to impinge on the exposed surface of the oil andtends to churn or mix. As has been explained above, this is undesirablewhen precision control is required.

The reservoir cylinders 34 and 35 are mounted close together on a singlebase and underneath a single top to form a single balanced unit. The oillines 51 and 52 are of equal length and, in general, the structure issuch that the total paths to the opposite sides of piston 53 are kept asshort and as equal as possible. It has been found that differences inthe pressure transmitted to the opposite sides of piston 53, due todifferences in frictional line drops, can have a significant effect. Bythus providing a unitary compact balanced and short line actuator 100,the possibility of imbalance in the pressure ultimately applied againstthe opposite faces of piston 53 is reduced. This balanced ultimatepressure is desirable where a stable condition is desired. Thus, inaddition to the visual check advantages of providing a unitary actuator1%, there is the advantage of a more easily produced stable condition.

The structure of dispersing head 1;; is best shown by' reference to thesectionalized view in FIGURE 1, and the view in FIGURE 2. The extensiontube 12 flares into a; major or head portion. The major portion isprovided with a plurality of channels 14. Each of these channels 14communicate with the hollow interior of extension tube 12. In theembodiment shown, four of the channels 14 are provided, spaced -degreesapart. As best shown in FIGURE 1, each channel 14 extends outwardly fromthe longitudinal axis of extension tube 12 so that each said channelforms an acute angle with extension tube 12.

The angle, of itself, is not critical, but this angle in relation to theother dimensions of the structure is critical to the preferred operationof the entire structure.

It has been found that if the angle between channel 14 and extensiontube 12 is so great that the stream of air passing from an air line intotube 12 and hence out channel 14 strikes a wall of the reservoir in adirect line from channel 14, there is a thrusting effect down the walland into the oil 64). It must be borne in mind that the applications towhich this structure is particularly suited, the opening and closing ofvalves to admit high pressures, vacuums, vents to atmosphere andshut-offs, are sudden and there is a consequent tendency to a blasteffect.

On the other hand, it has also been found that if the angle betweenchannel 14 and extension tube 12 is too acute, the air being directedrelatively sharply against the undersurface of top 30 tends to createturbulence. It has been found that this turbulent effect is notpreferred from the point of view of minimizing any disturbance of thefree surface of oil 60. Thus, it may be stated that as the angle betweenthe channel and the tube gets larger, the desirable baffling effectimproves until the point of which the direct blast of air from thechannel impinges directly on the wall, at which point, the baffiingeffect relatively suddenly decreases in effectiveness. It is thusapparent that the optimum angle between the channel 14 and the tube 12is that at which the longitudinal axis of channel 14, as extended,strikes the undersurface of top 30 near, but not at, the junction of thetop with the wall of the reservoir. Another way of stating the angulardisposition of channel 14 is to say that as installed in a reservoir,the angle of channel 14 is such that the major portion of a stream offluid directed through said channel would strike the top of thereservoir near, but not at or beyond, the junction of said top with saidwall. The same description can be applied to the dispersing heads at thebottom of the reservoirs except, that in this case, the major portion ofa stream directed through the channel would strike the bottom of thereservoir, rather than the top.

The total cross-sectional area of the four channels 14 is preferablygreater than the cross-sectional area of the interior of extension tube12. The reason for this is explained below. While four channels 14 areshown, and it has been found that these are satisfactory, it isunderstood that a greater number of channels can be used. While a lessernumber of channels might be operative, the desirable distribution andbafiiing affect is not as pronounced. For the purposes of this patent,the underside of the top 30 and the upper side of the base 40 may bedescribed as the end surfaces of the reservoir.

The use of the term turbulence above should not be taken as an impliedallegation that the flow is technically laminar when the preferredarrangement is used; the term is used to indicate that there is a moreviolent blast effect.

The use of the lower bafiies, which may be described as oil bafi les oroil dispersing heads, are important particularly where low viscosityoils or water are being used. In such conditions, when the oil or wateris flowing back into the reservoir, it tends to splash up and even enterthe air port, thence into the valving mechanism. This effect isparticularly pronounced when the sudden reversal of conditions involvesthe rapid change from a pressure applied to the surface of oil in thereservoir to a vacuum. It has been found that the provision of baflles,such as those described herein, prevent the 'water or oil from tendingto leap up the sides of the reservoir.

Previously known baffles have directed the fluids directly outwardly orto the side, so that they impinge directly on the walls of thereservoir. This type of baffiing does not eliminate the blasting orstriking of either gas or liquid, along the sides of the reservoir,which has been found to be a critical problem. The J-tube, as describedin the co-pending application, does improve over those baffles whichdirect the blast to the side, but the present invention is animprovement over the J-tuhe also. The present dispersing head requiresless criticality of centering in the reservoir, as compared to theJ-tube. A slight displacement from the center on the part of the I-tubetends to result in an unequal dispersion. The present dispersing headresults in a more even dispersion of the fluid over the entire endsurface than in other known baffles.

Another advantage of the present head is that the increasedcross-section-al area of the channels as compared to the tube asdescribed above, results in a decrease in the velocity of the fluid asit enters the reservoir clue to well-known physical principles. This isdesirable in re ducing the kinetic energy of the fluid.

It is understood that the use of only the top bafiles is advantageousand useful. In particular, where there are W viscosity oils or Water, ithas been found additionally useful to also provide the lower or oilbaflles. It is understood that even where higher viscosity oils areused, the lower baffles may be employed with some advantage, at least asa safety rfactor, and without any disadvantage.

The scope of this invention is to be determined by the appended claimand is not to be limited by the foregoing description and drawings whichare illustrative.

I claim:

A pneumatichydraulic actuator, comprising a reservoir cylinder having abottom end and a top end, a closed wall connecting said bottom end andsaid top end, each of said bottom end and top end having an innersurface, an oil line communicating with said reservoir cylinder throughthe inner surface of said bottom end thereof, an air line communicatingwith said reservoir cylinder through the inner surface of the top endthereof, each of said lines communicating with said cylinder through adispersing head, each said dispersing head having an extension tubecommunicating to and extending from one of said lines through one ofsaid inner surfaces into said reservoir cylinder, a plurality ofchannels in each said head communicating with said extension tube, eachof said channels having a longitudinal axis at an acute angle With saidextension tube. and pointing toward the said inner surface through whichsaid extension tube extends, and an extension of the longitudinal axisof each of said channels in a direction away from said extension tubeintersects said inner surface near the intersection of said innersurface with said wall.

References Cited by the Examiner UNITED STATES PATENTS 666,156 1/1901RidgWay 914 1,626,556 8/1927 Ridgway 137-209 2,123,809 7/1958 Seitz137592 2,849,987 9/1958 Shafer 91-4 SAMUEL LEVINE, Primary Examiner.FRED E. ENGELTHALER, Examiner. P. T, COBRIN, Assistant Examiner.

